Device for continuous casting of slabs

ABSTRACT

An apparatus for continuous casting of slabs having a considerably larger width than thickness, particularly of steel slabs with a thickness below 80 mm, includes feeding the molten material to a mold from a casting vessel, the mold having a cross-section at its charge and power inside, deviating in the middle portion from the desired casting format by a large cross-section but matches the desired format near the edges. In order to obtain an objective for providing equipment for making steel slabs with thickness below 80 mm, without defects and with a high surface quality, its is suggested that, while maintaining the cross-sectional contour of the charge and pour-in end of the mold, over the entire mold length, the skin of the emerging casting in its middle portion is deformed by directly downstream arranged guide and support structure such that after passage through the deforming path the surfaces of the entire slab coincide with the initial edge zone surfaces.

The present invention relates to a device for the continuous casting ofslabs which have a considerable larger width than thickness,particularly of steel slabs with a thickness below 80 mm, whereby moltenmaterial is poured from a casting vessel into a mold, having a chargeand pour-in cross-section, whose middle portion deviates from thedesired casting contour in a cross-section increasing fashion, butcorresponding to the desired casting format in the edge zone, andwhereby maintaining the cross-sectional format at the charge and pour-inside of the mold is maintained over the entire mold length, and thecasting skin as emerging from the mold is to be deformed in the middleportion, by means of guide and support means arranged directlydownstream from the mold such that following passage through thedeforming path, the surfaces of the entire casting are situated in thesurfaces of coinciding with the edge zone.

A mold for continuous casting of this kind is known from British PatentNo. A 1,199,805, whereby not only the crosssectional contour, but thecross-section itself, remains uniform from the entrance and charge endto the exit and discharge end of the mold. The final contour of thecrosssection of the continuous casting is formed exclusively throughrolls which are arranged downstream from the mold.

European Patent No. A 0,149,734, which corresponds to German Patent No.3,400,220, moreover, makes known a mold for continuous casting of steelstrip, wherein the wide sides form an upper funnel shaped pour-in andcharge zone.

This mold has the disadvantage that in the transition from across-section increasing pour-in zone, to the desired form and format ofthe continuous casting strong bending forces are exerted upon the skinof the casting within the mold. For reducing the wear resulting fromthis bending, it is necessary to maintain small the deforming anglealpha, while, in addition, the casting speed and the cooling speed haveto be selected within tight limits in order to make sure that the skincan be moved out of the mold without formation of cracks. Moldsconfigured in this fashion exhibit a strong friction in the transitionzone which friction can be reduced only to a relatively small extent bymeans of known lubrication. The known mold, moreover, has the additionaldisadvantage that upon maintaining a small deforming angle alpha,preferably smaller than 10°, the mold has to be made the longer thethinner the slab is supposed to be.

It is an object of the present invention to provide a method andequipment such that steel slabs with a thickness below 80 mm can bemanufactured without defects and with a high surface quality.

The object is attained in accordance with the invention by operation ofthe features which include the following cross-section in the middleportion of the casting is uniformly bulged, but is smaller on thedischarge at exit from the mold, as compared with a larger bulgecross-section at the pour-in and charge side, and that lines oftransition from the plane slab surface to the bulge surface has aconicity in longitudinal direction matching the cross-sectional andconicity increase of the bulging portion, but to be not more than 1.2%,that the spacing and distance from the outer periphery 18 of a castingpipe and spout, and the apex point of the bulge at the pour-in andcharge side in the surface level of the molten material is at least 20mm; that at least one roll of at least one pair of rolls of the guideand support means downstream from the mold is provided with sizingdimension matching the emerging casting; and that the distance betweenthe rolls of a roller pair from roller pair to roller pair reduces inthe direction of casting by at least 0.5 mm, but not more than 25 mm,such that the deformation at the front of solidification does not exceeda value of 0.5%.

The degree of bulging is selected in accordance with the invention suchthat in dependance upon the outer diameter of the casting spout andpipes, as used in the mold, it has a minimum distance of 30 mm to theapex point of the bulge on the entrance and charge side, the distancebeing taken in the level of the casting liquid in the mold. The lines oftransition in the mold concerning the bulge, to this part of the moldrunning in the plane of the slab surface is conically configured. Theconicity is matched in longitudinal direction to the cross-sectionalincrease of the bulging zone, but is never more than 1.2%.

The supporting guide means which are arranged downstream from the mold,are characterized in accordance with the invention in that at least oneroll, of at least one pair of rolls, is configured for sizing in amanner matched to the contour of the casting that emerges from the mold.Individual rolls may have a cylindrical, conical, or a bulgingconfiguration. They are resiliently suspended in a guide frame andhydraulically adjustable transversely to the axis of casting. In orderto make sure that the cold start-up casting can pass through the castingdeforming path without interference, one will use a known electronictrack or path control for the adjustment of the rolls.

The desired deforming of the casting, as emerging from the mold, isprovided in accordance with the invention such that the distance betweentwo rolls of a pair of rolls is reduced from roller pair to roller pairin the direction of casting by a value amounting to at least one halfmillimeter but not more than 25 millimeters. The range of widthadjusting of the rollers is required so that one can take intoconsideration requirements which are specific to the material used, aswell as requirements and conditions on the dimension in order to makesure that the product remains crack free. Reducing the bulge of theemerging casting format providing for the increase in cross-section,drawn to the flatness of the desired and final cross-sectional format ofthe casting, is preferably distributed over a total length of about atleast 11/2 meters such that only after the casting has left thedeforming portion of the casting withdrawal path the cross-section ofthe casting will be completely solidified, whereby this minimal value of1.5 m is associated with a distance reduction as between the rolls ofthe adjacent pair of 25 mm. The rolls, establishing the size, may beindividually driven.

The drawing illustrates an example of the invention, wherein FIG. 1 is alongitudinal section through the equipment for continuous casting;

FIG. 2 is a top view of the mold for slabs with a thickness of below 80mm;

FIG. 3 illustrates a section through the empty mold along the line 3--3of FIG. 2;

FIGS. 4, 5, and 6 show different configurations of the rolls,establishing the final dimension of the casting, the sections beingtaken along the line 1--1 in FIG. 1, particularly within the zone ofdeformation; and

FIG. 7 is a cross-section through the casting taken along the line 2--2in FIG. 1.

FIG. 1 illustrates a longitudinal section through the inventiveequipment for continuous casting of slabs with a considerable largerwidth than thickness, particularly steel slabs, with a thickness ofbelow 80 mm, whereby the molten material is poured from a castingcontainer 1 through a casting spout and pipe 2, dipping into the bath 4,the molten material being fed to this mold 3. The mold 3 is fastened toa frame 5 and may oscillate in the direction of casting, as indicated bythe arrows 6. The casting 7, having a format as illustrated, andemerging from the mold 3, is deformed in accordance with the inventionthrough downstream arranged support and guide means 8 of the castingsuch that the central portion of the skin 10 is situated in the plane ofthe casting surface of the edge zone 11.

As seen in top view, the mold 3 shown in FIG. 2, establishes inaccordance with the invention the outwardly bulging cross-sections 12and 13 establish in their middle portion, taken in conjunction withsmall side walls 14 corresponding to the desired casting format the moldcavity proper as between charge inlet and discharge outlet. The arrows15 and 16 are supposed to indicate that the longitudinal side walls 14,as well as the width defining side wall 17, are slidable, so that thedesired crosssection 7 can be adjusted in a variable fashion.

The dimension of the used casting pipe and spout 2 are related to thecross-section increasing bulge 12 in the middle portion on the chargeside of pour in such that in the surface level of the bath 4 of themolten casting material there is a minimum distance between the outerperiphery 18 of the casting spout and pipe 2, and the apex point of thebulge 19, amounting to 20 mm, and that distance is being maintained. Thelongitudinal section through the mold 3 along the line 3--3 in FIG. 2illustrates that the line 20 of the transition of the bulge, to the partsituated in the plane of the slab surface, runs conically, whereby, inaccordance with the invention, the value of the conicity remains below1.2%. Tee longitudinal side walls 14 are likewise conically adjusted,whereby through known spindles with different pitch, the desiredconicity is adjusted in dependence upon the width of the casting takentogether with the longitudinal shift 15.

Different configurations of the sizing roller pairs 8 of the roller pathare shown in FIGS. 4, 5, and 6, particularly in the zone of deformation.In FIG. 4 matching of the rolls 8 to the emerging casting 7 is obtainedin that two rollers 22, establishing a roller pair, have a concavelyformat sizing contour 23. In a second example of FIG. 5, cylindricallycontoured individual rolls 24, 25, and 26 approximate as a group thedesired size necessary for deforming the cross-section of the casting. Athird configuration is illustrated in FIG. 6, whereby the surfaces 27and 28, running parallel to the longitudinal plane of the casting, areprovided through the cylindrical rollers 29 and 30, while conicallycontoured rollers 31 are used for obtaining the transition surfaces 32.In this embodiment the rollers 29 to 31, establishing the size of thecasting, are situated on a common axis.

All of the individual rollers 22 through 26, and 29 through 31 providedfor working in the respective deformation zone, in all threeembodiments, are preferably resiliently suspended, and hydraulicallyadabtable. Matching the bulging cross-section 13 in the middle portionof the emerging casting to that of the desired casting format of theoriginal edge zones 11, is shown in FIG. 7. The guiding of the casting11, being completely solidified at this point, is taken over bystraight-through cylindrically contoured rollers 9.

I claim:
 1. Apparatus for continuous casting of slabs with considerablylarger width than thickness, particularly of steel slabs with athickness below 80 mm, including a casting pipe and spout for pouringmolten material from a casting vessel into a mold, the mold having acharge and pour-in cross-section, whose middle portion deviates from thedesired casting contour in a cross-section increasing fashion, the edgezones of the mold corresponding to the desired casting format thecross-sectional format at the charge and pour-in end of the mold ismaintained over the entire mold length, and the casting skin as emergingfrom the mold is to be deformed in the middle portion by means of guideand support means being arranged directly downstream from the mold suchthat following passage through the deforming path, the surfaces of theentire casting are situated in the surfaces of the edge zone; theimprovement comprising:the cross-section of the mold in the middleportion of the casting being outwardly uniformly bulged, but a bulgebeing smaller in a discharge and exit end from the mold, as comparedwith a larger bulge cross-section at the pour-in and charge end wherebygeometric lines delineating a transition from the plane slab surface ofthe mold to the bulging surface of the mold has a downwardly orientednarrowing tapering and conicity in longitudinal direction matching across-sectional and conicity increase of the bulging portion, but to benot more than 1.2%, a spacing and distance from an outer periphery ofthe casting pipe and spout and an apex point of said bulge at thepour-in and charge end in a surface level of the molten material is atleast 20 mm; at least one roll of at least one pair of rolls of theguide and support means downstream from the mold being provided withsizing dimension matching an emerging casting; and a distance betweenthe rolls of a roller pair from roller pair to roller pair reduces inthe direction of casting by at least 0.5 mm, but not more than 25 mm,such that any deformation at the front of solidification does not exceeda value of 0.5%.
 2. Apparatus as in claim 1, characterized in that atleast one of the roller pairs establishing the sizing is provided withits own drive.